1. Field
The present disclosure relates to an occupancy detection apparatus and a method for controlling the same, and more particularly, to an occupancy detection apparatus based on Impulse Response-Ultra Wide Band (IR-UWB), and a method for controlling the same.
2. Background
Offices, schools, clinics, a common living space in a house, and buildings provide necessary services to users. For example, a Heating, Ventilation, Air Conditioning (HVAC) system is a representative facility system that offers a service. Such a service is provided using an energy source like electricity or gas. Korea Energy Agency publicized the results of an analysis of energy consumption characteristics of each domestic sector in 2014, which reveal that a building sector occupies about 24.2% of the total domestic energy consumption, and the energy increase rate of the building sector is higher than an industrial sector and a transportation sector.
It is expected that the energy consumption of the building sector will further be increased due to the trend toward large buildings and enhanced convenience. Accordingly, reduction of energy in buildings may lead to a great decrease in total energy consumption. In order to reduce the energy consumption of a building without making users feel uncomfortable, more and more research has recently been conducted on intelligent control techniques for providing as much an illumination service and a heating and cooling service as needed only at a necessary time instant.
For intelligent control, energy consumption is estimated based on an energy consumption model and a service is controlled according to the estimated energy consumption, or a service is controlled based on a user's location. According to the energy consumption model-based estimation control scheme, a building under control and facilities (a chiller, a cooling tower, a pump, and so on) in the building are modeled, and an energy consumption is estimated. An optimum facility operation scheme is provided based on the estimated energy consumption, thereby saving energy. For this purpose, a technology of modeling a building and facilities in the building, and accurate indoor/outdoor state information about the building determined by means of various sensors (for sensing a flow rate, temperature/humidity, and so on) are required. To build this system in the building, the initial investment is huge.
According to the location-based control scheme, a service is provided based on the location of a user in a building. The illumination and cooling/heating of an empty space are turned off, and a service is provided adaptively to a place in which a user is located, thereby saving energy. Because a number of services may be provided by indoor location sensing, multi-sided research has been made to sense a motion of a person and locate the person in an indoor environment.
Conventionally, occupancy is detected by a sensor or Radio Frequency (RF). However, the conventional method has limitations in providing a service by detecting the accurate location and distance of an object in a large space due to its constraint in terms of installation of a plurality of sensors and accuracy.
FIG. 1 is a simplified conceptual view illustrating a conventional occupancy detection apparatus using a Passive InfraRed (PIR) sensor. The PIR sensor, also called a moving InfraRed (IR) detector, senses an object that radiates IR light. Every object having a temperature above the absolute temperature zero radiates IR light, and the temperature (36.5° C.) of a human body is representable within an IR range. The occupancy detection apparatus using a PIR sensor includes an IR radiator 10 and a light receiving sensor 30. IR light emitted from the IR radiator 10 is reflected from a person 20. The light receiving sensor 30 may sense reflected light 31, and accordingly determine whether there is any occupant.
Owing to its cheap price and sensitiveness to a motion, the PIR sensor is mostly used indoors. However, the high sensitivity of the PIR sensor to sun light, a flash, or temperature may lead to malfunction of the PIR sensor. Moreover, since the PIR sensor is capable of determining only the presence or absence of a moving object in a space, it is difficult to provide a per-location service in a large space with the PIR sensor. In other words, since the PIR sensor determines only the presence or absence of any person in a sensing space and does not determine the location of a person, the PIR sensor may not be used in a large conference room. Although a technique of conducting communication between PIR sensors has also been studied to locate a person in a large space, such a technique requires use of a plurality of PIR sensors.
FIG. 2 is a simplified conceptual view illustrating a conventional Impulse Response-Ultra Wide Band (IR-UWB)-based occupancy detection apparatus, and FIG. 3 is a graph illustrating the spectrums of a UWB scheme and other schemes, referred to for describing UWB. Referring to FIG. 2, the conventional IR-UWB-based occupancy detection apparatus includes at least three radar modules 41a, 41b, and 41c, and a controller 42. Each of the radar modules 41a, 41b, and 41c may include one transmission antenna and one reception antenna, output an impulse signal, and receive a reflected signal.
Referring to the frequency spectrums illustrated in FIG. 3, a UWB system 61 is designed by a wireless transmission technology in which digital data is transmitted in an ultrawide frequency band with very low power. The UWB system 61 has a relatively low spectrum across a very wide frequency band, compared to a conventional narrow band system 63 or a conventional wideband Code Division Multiple Access (CDMA) system 65. The UWB-based location sensing or occupancy detection scheme consumes low power and is robust against a jamming and multi-path environment. Due to its high accuracy of location detection, the UWB-based location sensing or occupancy detection scheme is widely used in determining an accurate distance.
UWB-based schemes are classified into a carrier-based scheme and an impulse-based (carrier-free) scheme. In general, a scheme of calculating a distance using the Time of Arrival (ToA) of IR reflected waves is often used. This takes the advantage of high distance measurement accuracy that UWB offers due to non-use of a carrier and use of very short pulses, such as nanosecond (nsec) pulses.
However, despite the high distance measurement accuracy, the conventional IR-UWB-based scheme suffers from an installation limitation in that a location can be determined only through a plurality of pieces of equipment. Referring to FIG. 2, conventionally, the three or more radar modules 41a, 41b, and 41c are installed indoors and information about a distance to an occupant 50 is collected through the radar modules 41a, 41b, and 41c, in order to determine the location of the occupant 50.
Since each of the radar modules 41a, 41b, and 41c includes a pair of transmission and reception antennas, it is capable of simply measuring only a distance. To locate the occupant 50 accurately, the distances measured by the radar modules 41a, 41b, and 41c should be subjected to triangulation. Therefore, the controller 42 should be additionally provided to collect sensing data from the plurality of radar modules 41a, 41b, and 41c, to thereby sense an occupant, and each of the controller 42 and the radar modules 41a, 41b, and 41c should have a communication module for communication. That is, the conventional occupancy detection scheme requires the three or more radar modules 41a, 41b, and 41c, for sensing the person 50, and additionally, the controller 42 for performing a positioning algorithm. As a result, the number of modules and cost for occupancy detection are increased.
Further, the conventional radar modules 41a, 41b, and 41c sense a distance of about 6 to 7 m. To sense the occupant 50 in a large space spanning 10 m or larger, a double or more of the sensors are required. To determine a distance and a location through a single device by dividing a large space into smaller zones without imposing constraints on users, hardware and an algorithm other than used in the conventional approaches need to be designed. In this context, active research is conducted on a technique of locating a user indoors through a single device to perform location-based control and thus save energy in a building.